Kate reveals kids are 'excited, a bit nervous' about coronation, as royals surprise fans camping out on The Mall

Royal fans camping out on The Mall ahead of the coronation have been rewarded with a surprise visit from not one but three senior royals.

King Charles, Prince William and Kate greeted crowds about three to four rows deep as they got out of their cars after leaving a lunch reception at Buckingham Palace on Friday, walking the rest of the way to a Commonwealth reception at Marlborough House.

The Princess of Wales offered an insight into how preparations were going for the royal family, revealing a few nerves – especially for their three kids, Prince George, nine; Princess Charlotte, eight; and Prince Louis, five.

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Prince George has a key role to play as a pageboy for his grandfather, the King, and all three Wales children will be a part of the procession back to Buckingham Palace.

"They're really well, thank you - excited, a bit nervous obviously with a big day ahead, they can't wait." she told a woman in the crowd who later identified herself as a BBC reporter.

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When asked how she and husband Prince William were feeling, the princess was remarkably honest.

"Yeah, all good hopefully," Kate began.

"[We're] a bit like swans - relatively calm on the outside and sort of paddling on the inside."

Kate added King Charles was "looking forward" to his big day and the trio were relishing the opportunity to be "saying hello to everyone who has stayed out so long".

Showing her caring side, the princess asked the journalist if she was tired and how she was coping with the coverage.

"It's long hours for everybody, isn't it but it'll be a great moment - a moment of celebration," Kate said.

Earlier in the line, as the camera cut to the Princess of Wales, she was overheard asking one woman to: "Please write in, I'd love to speak to you in the future."

When another presented her hand in a cast for the princess to shake, she looked shocked and had a chat about how the accident happened.

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Meanwhile, King Charles took his son and daughter-in-law to the other side of The Mall.

The monarch met with visitors from Australia, Italy, Thailand and America among others, seeming shocked and humbled to hear people had flown so far to witness his big day.

The surprise walkabout came after the Prince and Princess of Wales were seen chatting to Australian Prime Minister Anthony Albanese at a lunch reception inside Buckingham Palace on Friday.

Working members of the royal family attended the coronation eve engagement for governors-general of the realm and prime ministers.

This was followed by an informal reception in the gardens of Marlborough House, where the King was set to meet with Commonwealth leaders.

The King and his family where later scheduled to host the international royals who had arrived for the event.

Watch 9News' special coverage of King Charles' coronation for free on 9Now.